Pressure-generating device



Oct. 19, 1954 p KQPP 2,691,942

PRESSURE-GENERATING DEVICE Filed Sept. 14, 1949 4 Sheets-Sheet 1 78 [NYENTOR Phil 5 Ko a o Oct. 19, 1954 P. E. KOPP 2,691,942 PRESSURE-GENERATING DEVICE Filed Sept. 14, 1949 4 Sheets-Sheet 2 ATTORNEY Oct. 19, 1954 P. E. KOPP 2,691,942

PRESSURE-GENERATING DEVICE Filed Sept. 14, 1949 4 Sheets-Sheet 3 '74 62 it: 79 94 8 J 92 J I /1a I 80 [MENTOR I I Phil/,0 KOPP ATT RAE? Oct. 19, 1954 P. E. KOPP 2,691,942

PRESSURE-GENERATING DEVICE Filed Sept. 14, 1949 4 Sheets-Sheet 4 222 x 220 ii 3 Q? L66 .wwzvz'azz 64 J P/Ii/L Kopp 225 I I BY 14. 228 ATT RNE'Y Patented Oct. 19, 1954 UNITED STATES PATENT OFFICE PRESSURE-GENERATING DEVICE Philip E. Kopp, Springfield, Ill.

Application September 14, 1949, Serial No. 115,677

(Cl. l03-37) 8 Claims. '1

This invention relates to improvements in pressure-generating devices. More particularly this invention relates to improvements in devices that can generate hydraulic pressure.

It is therefore an object of the present invention to provide an improved device that can generate hydraulic pressure.

In the operation of machines that respond to hydraulic pressure to move and perform work, it is frequently desirable to supply a large volume of hydraulic fluid at low pressures to assure initial movement of the machines and then to supply a smaller volume of fluid at higher pressures to complete the movement of the machine and to exert the required final pressures. The combina' tion of large volumes of fluid'at low pressures and smaller volumes of fluid at higher pressures is very useful in the operation of hydraulicallyactuated jacks, presses, rivet squeezers, and ma chine tools. Various methods and apparatus have been proposed to assure large volumes of fluid at low pressures and to assure smaller volumes of fiuid at higher pressures; and one such apparatus consists of a pressure-generating device with a wobble plate that is mounted on a movable pivot. The wobble plate and its movable pivot will move automatically in response to changes in the output pressure, or they can be moved manually by the shifting of gears, to vary the length of stroke of the pistons of the pressure-generating device. Another such apparatus consists of a pressuregenerating device with a motor shaft that carries a crank arm and that is axially reciprocable to adjust the position of the wobble plate. Reciprocation of the motor shaft and its crank arm changes the inclination of the wobble plate and thus varies the length of stroke of the pistons of the pressure-generating device. Still another such apparatus is a pressure generating device that has a non-reciprocable motor shaft which carries a. wobble plate, and that has a reciprocable cone which can be moved to adjust the angle of inclination of the wobble plate; the cone being reciprocable to adjust the angle of inclination of the wobble plate and thereby adjust the length of stroke of the pistons of the pressure-generating device. Other such apparatus consists of pressure-generating devices wherein the strokes of the pistons are fixed but wherein variable flow is attained by shifting a rotary valve or by rotating sloping-end pistons. In these various pressuregenerating devices the variations in the output volume are effected by auxiliary mechanisms: the reciprocable motor shafts, the movable wobble plate pivots, the cones that adjust the angles of inclination of the wobble plates, or the rotary valves and pistons that can be shifted by auxiliary, pressure-responsive plungers or by manually operated gear trains. Ordinarily these auxiliary pistons and gear trains will work; but they are not infallible and they offer considerable opportunity for errors in their construction and operation. Moreover, those pistons and gear trains are often complicated and are always expensive. For these reasons, such pressure-generating devices are objectionable. The present invention obviates these objections by providing a pressure-generating device with a wobble plate that responds directly to the forces exerted on the pressure-generating pistons of the device to move and change the output volume of the device. With such a device the pressure-generating pistons will deliver a large volume of hydraulic fluid at low pressures, but will, when the output pressure of the device increases, automatically, shift the position of the wobble plate of the device and thereby cause a reduction in the output volume of the device. It is therefore an object of the present invention to provide a pressuregenerating device with pressure-generating pistons that can respond automatically to high output pressures of the device to shift the position of the wobble plate.

The present invention utilizes the shifting of the wobble plate to vary the output volume of the pressure-generating device by having that wobble plate act upon hollow pistons which have ports that can be uncovered during reciprocation of those pistons. Under low pressure conditions, the pistons will be in such a position that the ports 0'. the pistons will be covered throughout the entire reciprocation of the pistons; and under high pressure conditions, the pistons will automatically assume a position wherein the ports will be uncovered during a part of the reciprocation of the pistons. The uncovering of the ports of the pistons will permit part of the fluid pumped by the pistons to pass through those ports, thus reducing the amount of fluid delivered to the outlet of the device. A number of springs will bias the pistons toward a position wherein the ports will be covered throughout the entire reciprocation of the pistons; but when the outlet pressure of the device is greater than the pressure exerted by the springs, the pistons will shift until the ports are uncovered during a part of the reciprocation of the pistons. As the outlet pressure continues to increase, the pistons will shift still further to uncover the ports for a greater part of their reciprocation. It is therefore an object of the present invention to provide a pressure-generating device with hollow pistons that have ports which can be uncovered during part of the reciprocation of the pistons.

The pressure-generating device provided by the present invention has a cam that is splined to an intermediate shaft which is keyed to the shaft of the power source, usually an electric motor. This cam will normally respond to the action of the springs to move against the ends of the pistons; and as it rotates, this cam will successively force the pistons to telescope into the cylinders of the pressure-generating device. When the pressure at the discharge port of the device increases, the pistons will resist the forces exerted upon them by the cam and will cause the cam to move along the intermediate shaft. The splines permit such movement while maintaining rotation of the cam. It is therefore an object of the present invention to provide a splined cam that is supported by an intermediate shaft and is movable along that shaft in response to pressures exerted on the pressure-generating pistons of the device.

Each of the cylinders for the pressure-generating device of the present invention consists of two parts; the upper part being a hard metal sleeve and the lower part being a combination cylinder extension and valve housing. Both parts are held in cylindrical openings in the body of the device; and each cylinder is provided with fluid-tight seals which prevent leakage of fluid past that cylinder. Additional seals are provided in the body of the pressure-generating device, adjacent the inlet and discharge valves, to prevent passage of fluid past those valves. Those seals are so constructed that they will positively prevent escape of fluid between surfaces which are carefully machined, but which are not ground and lapped. As a result, the body of the pressure-generating device provided by the present invention need not be ground and lapped. This greatly decreases the cost and time of manufacture since only the cylinders, pistons, valve elements and valve seats need be ground and lapped. With such a construction it is possible to generate and confine pressures as high as twenty thousand (20,000) pounds per square inch. It is therefore an object of the present invention to provide seals that prevent leakage of fluid past the hard metal sleeve cylinders and past the valve seats of a pressuregenerating device; such seals being capable of coacting with machined surfaces to prevent leakage of fluid.

The body of the pressure-generating device provided by the present invention is made of one piece of metal, and it has bores therein to receive the cylinders, valve seats, and valve elements. By making the body of one piece of metal, the present invention avoids leakage due to stretched bolts and leaky gaskets, and it obviates the need of grinding mating faces of adjacent sections of bodies. Moreover, by being made of one piece of metal into which the cylinders, valve elements, and valve seats are fitted, the body of the pressure generating device can be made of lightweight metal. It is therefore an object of the present invention to provide a one-piece body for pressure-generating devices.

The pistons provided by the present invention will have a constant length of stroke, and the Wobble plate will have a constant angle of inclination. In addition, the axis of the wobble plate, and the axis of the driving cam therefor, will intersect in the piston-engaging plane of the wobble plate. Such an arrangement makes it possible to form right-circular cones on the ends of the pistons, and to make the angle of development of those cones equivalent to the angle of inclination of the wobble plate. Where this is done, line contact rather than point contact is assured between the wobble plate and each piston, virtually noiseless operation is assured, and virtually all wear is eliminated. It is therefore an object of the present invention to provide a wobble plate of fixed inclination, pistons of constant stroke, a piston-engaging plane on the wobble plate that includes the intersection of the axis of the wobble plate and the axis of the supporting shaft, and right-circular cones on the pistons that have an angle of development equivalent to the angle of inclination of the wobble plate.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description several preferred embodiments of the present invention are shown and described but it is to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing Fig. 1 is a plan view of the one-piece body of a pressure-generating device that is made in accordance with the principles and teachings of the present invention,

Fig. 2 is a view of the bottom of the body which is shown in Fig. 1,

Fig. 3 is a cross-sectional, side View of the pressure-generating device of which the body of Figs. 1 and 2 is a part, and it is taken along the plane indicated by the line 3-3 in Fig. 1,

Fig. 4 is a cross-sectiona1 side view of a portion of the device of Fig. 3, and it is taken along the plane indicated by the line 4d in Fig. 1,

Fig. 5 is a plan view of a recessed annular plate which is incorporated in the device of Fig. 3,

Fig. 6 is a cross-sectional side view of a modifled form of pressure-generating device contemplated by the present invention.

Fig. 7 is a cross-sectional side View of another modified form of pressure-generating device contemplated by the present invention,

Fig. 8 is a cross-sectional view of another form of piston and cylinder usable with the pressuregenerating devices contemplated by the present invention, and

Fig. 9 is a cross-sectional view of still another form of piston and cylinder.

Referring to the drawing in detail, the numeral it! generally denotes the body of a pressure-generating device that is made in accordance with the principles and teachings of the present invention. The body I ii is cylindrical in form and it is made from one piece of metal. Ordinarily that body will be made of steel; but where reduced weight is desired, as in aircraft, the body It! can be made of aluminum, magnesium, or alloys of those metals. The body is has a chamfer I2 at the periphery of the upper face thereof, and it has a shoulder i l on that upper face which is spaced inwardly of the chamfer I2. A central recess iii is formed in'the upper face of the body In; and a secondary recess E8, of smaller diameter and less depth, is provided at the base of the recess 95.

Spaced outwardly from the central recess l6 are four cylinder-receiving bores 20. These bores extend downwardly from the upper face of the body It! and they have lower portions 22 of larger diameter. The lower portions 22 extend upwardly from the lower face of the body, and they coact with the upper portions of bores 20' to provide abrupt shoulders in the body 10.

The lower end of the lower portion 22 of each of the bores 20' is provided with threads 24 opening to the lower face of the body it. The four cylinder-receiving bores 20 are equally spaced from the central recess l6, and each bore 20 is equally spaced from adjacent bores 20.

Also spaced outwardly from the central recess I6 are four valve-receiving bores 25. The radial distances between the valve-receiving bores 25 and the central recess I5 are greater than the radial distances between the cylinder-receiving bores 20 and the central recess It. The valvereceiving bores 26 are equally spaced from each other; and their centers define straight lines which pass through the centers of the cylinderreceiving bores 20. Each of the valve-receiving bores 26 is spaced equally from adjacent cylinderreceiving bores 28. The valve-receiving bores 26 extend upwardly from the lower face of the body H], but they do not extend completely through that body. Larger diameter, lower portions 28 of the bores 25 extend upwardly from the lower face of the body It the upper and lower portions of the bores 26 forming abrupt shoulders within the body [0. Threads 35 are provided at the lower ends of the lower portions 28 of the bores 25, and those threads open to the lower face of body It.

The diameters of the cylinder-receiving bores 20 and the valve-receiving bores 26 are preferably identical, and the diameters of the lower portions 22 and 28 of bores 25 and 26 are also preferably identical. Where this is the case, the number of difierent tools that must be used in forming the bores in body H) can be kept at a minimum. This not only reduces the number and kind of tools, but it also reduces the number of times the body ll) must be handled during its manufacture. All of this leads to reduced cost.

An annular groove 3| is formed in the body I 0 adjacent each of the lower portions 22 of bores 20, and the grooves 31 open into those lower portions 22. An annular groove 33 is formed in the body It) adjacent each of the lower portions 23 of bores 25, and the grooves 33 open into those lower portions 28. Ducts 32 extend between the annular grooves BI and 33, and thus those ducts connect the bores 20 with the bores 25. The annular grooves 13! and 33 can be made by inserting a cutting tool into the body it through the bores 20 and 26. The ducts 32 are conveniently formed by drilling holes from the exterior of the body it to bores 26, and then drilling smaller holes from the bores 28 to the bores 20.

The larger of the drilled openings will, in each instance, be closed by cylindrical plugs 34. Those plugs will be pressed into the larger of the drilled openings and then will be welded to the body Hi. The plugs 34 will be made short enough so their inner ends terminate short of the'bores 26. By this method, the ducts 32 can be made cheaply and simply while retaining the liquid-tight character of the body ID.

A discharge port 36 is provided at the center of the body Ill, and that port opens to the bottom face of that body. Threads 38 are provided at the bottom of the discharge port 36, and those threads will receive a high pressure line, not shown, which will extend to the machine operated by the hydraulic fluid from the pressuregenerating device. Four ducts 40 extend from the bores 26 to the discharge port 36; and those ducts are conveniently formed by drilling two radial openings from the exterior of the body I0 through the bores 26. Each of the drilled holes will pass through a bore 26,, through the discharge port 36, and then terminate at a second bore 26. Once the ducts 40 have been formed, plugs 42 will be pressedinto the outer ends of the drilled holes and welded to the body 40. The plugs 42 will be short enough to terminate short of the first bore 26. By this method, the ducts 40 can be made cheaply and simply while retaining the liquid-tight character of the body l0.

Four axially-directed holes 44 are provided in the body It] for receipt of the shanks of machinescrews 45. Those holes are contiguous with holes 46 of larger diameter; holes 46 receiving the heads of the screws 45. The screws 45 will preferably have slots across the tops thereof to receive the blade of a screw driver, and that screw driver can be inserted through the holes 46 to rotate the screws 45.

A chamfer 48 is provided at the periphery of the lower face of the body l0. That chamfer, together with chamfer l2, shoulder I4, recesses l6 and I8, the upper and lower portions of bores 21! and 26, threads 24, 30 and 38, annular grooves 3| and 33, ducts 32 and 40, discharge port 36, and holes 44 and 46 can all be made by usual and customary machining methods. None of these portions of the body In requires grinding or lapping; consequently the body It] can be made quickly and cheaply by mass production methods.

The body ill will receive the cylinders, pistons, valve elements, and valve seats of the pressuregenerating device; and it will maintain all of those component parts in properly spaced, leakproof relation. Each of those parts can be made individually and then assembled with the body It]. Thus, the pressure-generating device provided by the present invention lends itself well to manufacture on a sub-assembly basis.

A sleeve 50, preferably of hard steel, is inserted in the upper end of each of the cylinder-receiving bores 20. The sleeves 50 have flanges at the lower ends thereof, and those flanges will seat solidly against the shoulders between the upper and lower portions of the bores 25. The tolerances between the sleeves 5t] and the bores 28 will be such that the sleeves can be pressed into position in those bores. The inner surfaces of the sleeves 50 will be ground and lapped to receive exteriorly ground and lapped pistons 52. These pistons will preferably be of hard steel, and they will have axially-directed bores 54 extending upwardly from the lower ends thereof. The axial bores 54 terminate a short distance below the upper ends of the pistons 52 by merging with transversely-extending bores 55. Each of the pistons 52 has four bores 5 extending through to the annular ports 5'! at the surfaces of the pistons 52. By being ground and lapped, the pistons 52 and the sleeves 5!) will have extremely close tolerances and will be capable of confining fluids under heavy pressures while permitting telescoping movement of the pistons relative to the sleeves.

A smaller diameter section is provided at the bottom of each of the pistons 52, and that section coacts with the rest of the piston to provide an abrupt shoulder 58. The shoulders 58 of the pistons 52 receive and hold washers so; the washers 65 projecting slightly beyond the peripheries of the pistons 52.

A combined check-valve housing and cylinderextension 62 of cylindrical form has an upper portion 6i provided with threads; that portion being spaced from the rest of housing 62 by an abrupt shoulder Ill. The sleeves 50 and the upper ends of the housings 62 constitute the cylinders in which the pistons 52 reciprocate; those pistons being held closely by the sleeves 5i). The threads on the upper portion of each housing 62 can be threaded into the threads 24 at the lower ends of the bores 20. The upper ends of the check-valve housings 62 are provided with axially-extending annular projections E l. Those projections will receive and hold rings 66. The height of any one of the annular projections t l is less than the thickness of any one of the 0 rings 66; and when the upper portions of the check-valve housings 62 are threaded into the threads 24 of lower portions 22, the 0 rings 68 will be compressed by their engagement with the flanged lower ends of the sleeves 52. Those 0 rings will coact with the flanged lower ends of sleeves D, with the annular projections 64, and

with the inner surfaces of the bores 20 to provide fluid-tight seals in the body it). These seals will be primary seals, and they will keep hydraulic fluid from leaking upwardly between the exterior surfaces of sleeves 59 and the inner surfaces of bores 20. The engagement between the flanges on sleeves 50 and the shoulders between the upper and lower portions of bores 22 will provide secondary seals; and those seals add to the sealing effect of 0 rings 66.

The shoulders on the check-valve housings 62 will limit the upward movement of the annular projections 64 on those housings. When fully seated against the lower face of the body It, the shoulders ill on the check-valve housings 52 will hold the annular projections 64 of those housings approximately four one thousandths (0.004) of an inch below the flanged lower ends of the sleeves 50. This arrangement assures heavy compression of the 0 rings 66 while assuring full seating of shoulders 16 against body [0. That full seating of shoulders l0 against the lower face of body I0 is used to provide primary seals which will keep hydraulic fluid from leaking down along the threads 24 of the body [0.

A transversely-extending duct 68 is provided in each of the housings 52, and those ducts extend completely through the walls of the housings 52. The ducts 68 are located so they register with the annular grooves 3i in the body It. The transversely-extending ducts 58 are contiguous with the axial bores 72 in the check-valve housings 62.

An inwardly directed flange M is located adjacent the lower end of the axial bore 72 in each of the check-valve housings 62, and those flanges will receive the lower ends of the helical compression springs it. The upper ends of the helical compression springs 16 will bear against the washers Ell on the pistons 52, and will bias those pistons upwardly. The lower ends of the pistons 52 extend within the upper ends of the helical springs 16, thus keeping the helical springs and pistons in assembled relation.

A ground and lapped seat 18 for a ground and lapped ball 82 is provided at the lower end of each of the check-valve housings 62; the seats 18 being held against shoulders 79 in the housings 62 by retaining rings 80. The retaining rings 89 are provided with hexagonal recesses to receive wrenches, and those rings will be threaded into the bottoms of the check- 8 valve housings 62. The engagement between the valve seats 18 and the shoulders 79 will be so tight that hydraulic fluid will be unable to leak past the exterior surfaces of the seats 18. The balls 82 will be disposed above the seats 18, and they will normally be held in engagement with those seats by spiral compression springs 84 which have their upper ends bearing against the flanges It. The engagement between the balls 82 and the seats '68 will be intimate enough to prevent leakage of hydraulic fluid when the balls are on the seats.

With this arrangement hydraulic fluid within the cylinders, formed by sleeves 50 and the upper ends of the check-valve housings 32, will positively be held against escape upwardly pastthe exteriors of sleeves 50 by 0 rings 66 and by the engagement between the flanges on those sleeves and the shoulders between the upper and lower portions of the bores 20. That fluid will also be held against escape upwardly by the close fit between pistons 52 and sleeves 50; and it will be held against escape downwardly by the engagement of shoulders 10 with body E0, the engagement of shoulders l9 with seats i8, and the engagement of balls 32 with seats 18. The only avenues open to fluid attempting to escape from the cylinders formed by sleeves 50 and housings 62 will be through ducts 68, grooves 3i and ducts 32.

A spiral spring 86 is located in each of the valve-receiving bores 26, and those springs normally press ground and lapped balls 88 downwardly against the ground and lapped valve seats 00 within the lower portions 28 of bores 26. The valve seats 90 are held against the shoulders between the upper and lower portions of bores 25 by the conjoint action of 0 rings 96 and retainers 92. Axially-directed annular projections 94 are formed on the upper ends of the retainers 32, and each of those projections is shorter than the thickness of any one of the 0 rings 96. The annular projections 9d are so dimensioned that when the shoulders 93 of the retainers 32 are seated against the lower face of the body E0, the upper end of each of the annular projections 94 will be spaced four one thousandths (0.004) of an inch below the adjacent valve seat 90. This makes possible heavy compression of the 0 rings 96 while permitting full seating of shoulders 93 against body it. The heavy compression of 0 rings 35 enables those rings to positively prevent leakage of fluid downwardly past the lower face of valve seats 90, and also presses the seats 90 against the shoulders between the upper and lower portions of bores 25 with sufficient force to provide an initial seal. The full seating of the shoulders 93 against the lower face of body I!) will provide positive and primary seals against the leakage of fluid along threads 30.

Each of the retainers 92 has an axial bore 98, and that bore will register with the central opening of the adjacent valve seat 90. Extending radially outwardly from the bore 98 in each of the retainers 92 are four holes I00. These holes are in register with the annular grooves 33 in the body It. Consequently, fluid passing from the bores 20 through the ducts 32 to the grooves 33 can pass into the bores 98 of the retainers 92 through the four radially-directed holes I00.

The 0 rings will coact with the bores 26, seats 90 and projections 94 of retainers 92 to prevent leakage of fluid downward along the exterior of seats 90 while balls 88 will coact with the seats 90 to prevent leakage of fluid between 9 balls and seats; and shoulders 93 will coact with body I to keep fluid from leaking downwardly past threads 30. Consequently, the fluid from ducts 32 can only flow uni-directionally upwardly past balls 88 and into ducts 40.

When the sleeves 50, the pistons 52, the 0 rings 06, the check-valve housings 02 with their springs, seats and balls, the springs 06, the balls 88, the valve seats 00, the 0 rings 90, and the retainers 92 are assembled with the cylindrical body I0 an integrated and unitary construction results. This construction will have fluid-tight integrity without any need of the gaskets customarily employed in the multi-section bodies of pressure-generating devices, and it eliminates the bolts customarily used to hold multi-section bodies in fluid-tight relation. In this way, the present invention avoids the troublesome leakage through gaskets and stretching of bolts experienced with multi-section bodies.

A cam housing I02 is constructed so it can engage the upper face of the cylindrical body I0. That cam housing has an annular face I04 that will surround and press against the shoulder I4 on body I0; and that face I04 will form a fluidtight seal with the upper face of the body I0. The annular face I 04 of the cam housing I02 will have four threaded openings I06 therethrough, and those openings will be in register with the openings 44 in body I0. The machine screws 45 will extend through the openings 46 and 44 and will then be seated in the threaded openings I00.

The upper end of the cam housing I02 has an end face I I0 and a recess II 2 in that end face. The end face H0 and the recess II2 receive the end face of an end bell II4 of an electric motor; the recess II2 receiving and centering a circular projection III; on the end face of that end bell. The motor will have a rotatable shaft H7, and that shaft will have a key slot to receive a Woodruff key II 5.

The cam housing I02 has a cylindrical bearing seat I03 adjacent the upper end thereof, and that bearing seat receives and holds the outer race of an anti-friction bearing I20. The inner race of the bearing I20 is pressed over a stud-carrying plate I22. The plate I22 carries six studs I24 which are all located on or to one side of the center line of the stud-carrying plate I22. The studs I24 are spaced thirty-six (36) degrees apart; the centers of the most remote studs lying on the center line of the plate I22. The lower ends of the studs I24 are chamfered, and those ends extend within helical compression springs I20. The studs I24 will guide and center the springs I20 and will hold those springs in assembled relation with the stud-carrying plate I22. The lower ends of the helical springs I20 will extend into recesses I30 in a recessed annular plate I28. There are six recesses I30 in the annular plate I20, and those recesses are in register with the six studs I24 carried by the stud-carrying plate I22. I-Ioles I32, of lesser diameter than the recesses I30, are located in the bottoms of the recesses I30; and those holes permit fluid to drain out of the recesses I30.

The recesses I30 all are located on or to one side of the center line of the annular plate I28, and they are spaced apart thirty-six (36) degrees. Three balancing holes I34 are located in the other half of the annular plate I20; those balancing holes compensating for the removal of metal experienced in forming the recesses I30 and the holes I32. The weight of metal removed in forming the holes I34 should equal the difi'erence between the total weight of the studs I24 and springs I20. The balancing holes I34 will be equi-spaced in the other half of the annular plate I28, as shown particularly in Figure 5, and the holes I34 will have their centers at the same distance from the axis of annular plate I20 as are recesses I30 and holes I32. With this arrangement the stud-carrying plate I22, the annular plate I28, studs I24, and the springs I20 will be statically and dynamically balanced.

The recessed annular plate I23 is pressed onto the upper end of a cam I36; and that cam has splines I00 at the interior surface thereof. Those splines will interflt with and be supported by splines I44 on an intermediate shaft I40 which has a bore I42 that telescopes over the motor shaft III. The Woodruff key II5 will positively maintain the intermediate shaft I40 and the motor shaft ill in assembled relation, and the splines I38 on the cam I30 will coact with the splines I44 on the intermediate shaft I40 to transmit rotation to cam I36 while permitting that cam to reciprocate along the intermediate shaft I40.

The lower end of the intermediate shaft I40 will be pressed into the inner race of an antifriction bearing I 40; and the bearing I40 will coact with the bearing I20 to guide and support the intermediate shaft I40. A spacing ring I43 will extend between the inner race of the bearing I40 and the lower end of the cam I36; that ring limiting downward movement of cam I30. That cam will be able to move upwardly along the intermediate shaft I40 while being driven by the splines I44 and I38.

The cam face of cam I36 is an annular surface inclined at an angle of eighty-one (81) degrees to the axis of the cam; and a generally-cylindrical portion I3? projects perpendicularly downward from that surface. The cam surface and the generally-cylindrical portion I3'II' receive and hold the upper race I00 of a combination wobble plate and anti-friction bearing. Balls I02 will bear against the upper race I50 and will also bear against the lower race I54. The lower face of the lower race I 54 will be ground flat, and it will bear against the upper ends of the pistons 52. The upper ends of the pistons 52 are ground and lapped to form right-circular cones which have an angle of development exactly equal to the angle of inclination of the wobble plate. That angle will be the same as the angle of inclination of the cam face: eighty-one (81) degrees. As a result, the lower face of the lower race I 54 will be precisely parallel to the upper ends of the pistons 52. In addition, the axis of the cam I30 and the axis of the generally-cylindrical portion I3? will intersect in the piston-engaging plane of the wobble plate. Such an arrangement makes it possible to have line contact rather than point contact between the pistons and the wobble plate makes it possible to have virtually noiseless operation, and makes it possible to greatly minimize wear.

A return duct I53 is provided in one wall of the cam housing I02, and the upper end of that duct is provided with threads I58 to receive thereturn line from the machine operated by fluid from the pressure-generating device. A number of ports Iii'l are located in the wall of the cam housing I02 above the level of cam I30. The cam housing will be set in a reservoir. of hydraulic fluid, not shown, and the level of fluid in that reservoir must be above the bottoms of the checkvalve housings 62.

When power is applied to the motor, the motor shaft II'I' will rotate; and. that motor will, through the action of Woodruff key H5, rotate the intermediate shaft I 30. The shaft His) will rotate the stud-carrying plate I22, cam I35, recessed annular plate I 28, and the upper race 150. The springs I25 will be stressed to bias the cam I 35 against the spacing ring 148; and at low fluid pressures in the cylinders, the cam will rest against the ring M8. When the cam I36 is resting against the ring I58, rotation of that cam will cause the upper race I50 and balls I52 to force race I52 to produce a wobbling action. In the course of that wobbling action, the plate I54 will successively urge each of the pistons 52 downwardly against the action of springs I6. At any instant, two of the pistons 52 will be moving downwardly because of the action of lower race I55, and the other two pistons will be moving upwardly because of the action of springs 76. The lower race i 54 of the wobble plate will not rotate but will wobble as the upper race I 50 rotates with cam I35.

As the cam I35 continues to rotate, each of the plungers 52 will be moved upwardly and downwardly; the downward movement being due to the pressure exerted by the springs I25 upon the cam I36, and the upward movement being due to the springs 76 within the check-valve housings I52. The studs I24 and the springs I26 are located on that side of cam I35 which moves the pistons 52 downwardly; thus the upwardly and downwardly acting forces on the cam 35 are directly opposite each other. With this construction there will be no bending moments in the intermediate shaft I00, and no undue horizontally-acting forces on the bearings I20 and H35.

As the pistons 52 move upwardly, they will create a suction in the bores 12 which will raise the balls 82 off of the seats I8 and draw liquid into the bores 12. The liquid will flow into the bores '52 through the conjoint action of gravity and the suction caused by raising the pistons. When the pistons 52 start downwardly, under the force exerted by springs I26 and transmitted to the pistons by the wobble plate, the balls 82 will quickly seat on the valve seats I8 and prevent liquid flowing downwardly past those seats. Further downward movement of the pistons 52 will force liquid outwardly through the transverse ducts 58 in the valve housings 62, through the annular grooves 3!, through the ducts 32, through grooves 33, through holes I00, through passages 98, and upwardly past the balls 88 and seats 50 into ducts 50. In passing the balls 88, the liquid will raise those balls off of the seats 90; and then when the pistons 52 start upwardly again the balls 88 will quickly seat against the valve seats 90. On the next upward strokes of the pistons 52, the balls 82 will be raised off of their seats and additional charges of liquid will enter the bores 72 of the housings 52; and the additional charges of liquid will be pumped through the transverse ducts 68, the grooves BI, the ducts 32, the grooves 33, the holes I00, the passages 98, and past the balls 88 and seats 90 into the ducts 40.

The motor will rotate at high speed; and the pressure-generating device will, through its four cylinders and pistons, provide an almost pulsefree flow of liquid to the discharge port 36. The amount of liquid delivered to the discharg port 35 will vary as the pressure of the liquid at that port varies; and that pressure will vary as the load on the machine operated by the liquid varies As the pressure on the fluid increases, the fluid in bores 12 will offer increased resistance to the pistons 52, and those pistons will cause compression of the springs I26. The compression of springs I25 will act to increase the force upon the pistons 52 and thus increasethe force upon the fluid delivered to the discharge port 36. As the pressure on the fluid continues to increase, the springs I25 will continue to yield, and that yielding will permit the cam I36 to move upwardly along the intermediate shaft I 50. Such upward movement of cam I36 will permit the pistons 52 to shift their paths of reciprocation upwardly relative to the cylinders 50. At low pressures those paths of reciprocation will permit the annular ports 51 to be wholly covered by'the cylinders formed by sleeves 50 and housings 52. higher pressures the paths of reciprocation of the pistons 52 will have been shifted upwardly so the ports 51 in the pistons 52 may be partially uncovered during the upper parts of their strokes. Where this occurs, a portion of the liquid within the axial bores 54 of the pistons 52 will be 8X? pelled from the pistons and into the cam housing 382 as the pistons 52 move downwardly. This bypassing action will stop as soon as the ports 51 are covered by the sleeves 50. As a result, the pistons 52 will, at high pressures, pump for only a portion of their strokes; the ratio of the lengths of the pumping and non-pumping portions of the strokes being determined by the pressure on the liquid and the resultant yielding of the springs i20. When the pressure on the liquid approaches its upper limit, the springs I26 will be compressed so full that the ports 57 in the pistons will be covered only briefly during each stroke. sequently, most of the fluid raised upwardly by the plungers 52 in their upward movement will be expelled into the cam housing 02, and very little fluid will be pumped downwardly for delivery to discharge port 30. However, that liquid which is delivered to discharge port 35 will be under very heavy pressure. With this construction, the pressure-generating device will provide a variabl flow under variable pressure; exactly what is needed for jacks, presses, rivet squeezers, and machine tools.

One pressure-generating device made in accordanc with the principles and teachings of the present invention had plungers reciprocable through a five sixteenths inch stroke; and with a motor rotating at seventeen hundred and fifty (1750) revolutions per minute those pistons provided one hundred and ten cubic inches of fluid per minute at one thousand (1000) pounds per square inch pressure. Upon an increase in the discharge pressure from one thousand (1000) to five thousand (5000) pounds per square inch, the flow decreased automatically to twenty two .(22) cubic inches per minute. That flow was maintained indefinitely as long as the pressure remained at five thousand (5000) pounds per square inch; that fiow increasing to one hundred and ten (110) cubic inches per minute when the -pressure was relieved.

, indirectly lubricate the'upper bearing I 20 by splashing about within the housing. The liquid will eventually rise to the level of the ports I51,

and it will then spill out into the reservoir in which the cam housing 02 and the body I0 are positioned. One advantage of having the ports Con-' I51 above the level of the cam I36 is that the annular port 51 of the pistons 52 will always be surrounded by liquid and cannot become filled with air. The filling of those ducts with air would provide an air cushion within the pistons which would seriously affect the operation of the device. However, such air pockets cannot possibly form.

The ports I57 perform an additional function. The fluid returning from the machine operated thereby will be moving at a relatively high rate of speed and will tend to entrain air bubbles' That fluid will enter the chamber I02 and will begin to lose speed. Eventually, that fluid will find its way to the various ports I57 and will pass into the reservoir. Th size and number of the ports I51 will be such that the fluid passing therethrough and into the reservoir will be moving at a much slower rate than it did when it passed through duct I 56. In its travel at the lower speeds, the fluid can yield its entrained air bubbles.

Selection of the proper strength and size of springs I26, and selection of the proper diameters and strokes of pistons 52 will produce a pressuregenerating device capable of delivering the desired volume of liquid at the desired pressure. Such devices can be used to provide prompt and automatic delivery of liquid at the various desired pressures.

If desired, as shown in Fig. 6, the variable flow feature of the pressure-generating device can be omitted. In such cases, a body I62 is substituted for the body ID. All parts of the body I62 will be identical to the parts of body In except for the elimination of shoulder I4 and the substitution of recess I63 for recesses I6 and III. The exact same cylinders, rings, check-valve housings, springs, valve seats, balls, and retainers will be used as are used with body I6.

The body I62 will flt into a recess H0 in a cam housing I66, and it will be suitably secured to that cam housing by bolts, not shown. The cam housing I66 will have overflow ports I68, and it will have a return duct I92 the outer end of duct I92 being provided with threads WI. The upper face of cam housing I66 has a recess I72 and that recess will receive and positively center the end bell I'M of a motor. The cam housing I66 has a bearing seat I76, and that bearing seat will receive and hold an anti-friction bearing H8. The outer race of that bearing will be pressed into-the seat H6, and the inner race will be pressed over the upper end of the cam I86. The cam face will be inclined at an angle of eighty-one (81) degrees to the axis of the cam, and it will support a race I86. This race will coact with the balls I88 and the lower race I 90 to provide a combination anti-friction bearing and wobble plate. The lower face of the lower race I96 will be ground and lapped and will bear against the upper ends of the pistons I66. Pistons I 64 have the same general shape as pistons 52 but they are solid. Cam I86 is secured to motor shaft I66 by Woodruff key I82.

This construction possesses most of the desirable characteristics of the construction shown in Figs. 1-5. The only feature which is not possessed by this construction but which is possessed by the construction of Figs. 1-5 is the spring-supported cam plate and the hollow pistons. The construction shown in Fig. 6 is inexpensive, compact and simple.

Fig. 7 discloses a pressure-generating device which has a body I96 with four cylinder-receiving bores I98- Instead of opening to the upper surface of the body, as do the cylinder-receiving bores 20 of body I6 in Figs. 1-4 and of body I62 in Fig. 6, the bores I68 open into coaxial bores 260 in the body I66. The bores 200 are connected together by ducts 262, and a central bore .264 extends between the ducts 202 and the upper face of the body I96. The bores I98 will receive sleeves 50, 0 rings 66, and check valve housings 62 with their springs, seats, and balls. The body I96 will have bores 26 with their balls, seats, 0 rings, springs, and retainers; and it will have ducts between bores 26 and 26 and between bores 26 and discharge port 36.

The bores 206 will confine and guide springencasing slides 266. These slides have axial bores that receive helical springs 206; the upper ends of those springs bearing against the upper ends of the bores within the slides 266. The lower ends of the springs 208 will bear against flanges at the lower ends of pressure-distributing sleeves 2m; and the lower ends of the sleeves 2H3 will bear against the upper ends of pistons H2. The pistons 2I2 will be closely similar to the pistons 52 of Figs. 3 and 4 except that the upper ends of those pistons are flat. The slides 266 have projections *2 I I at the upper ends thereof, and those projections will engage the lower race 266 of a combination wobble plate and anti friction hearing. This wobble plate and anti-friction bearing will be mounted on a cam I86 which in turn is keyed to the shaft I86 of a motor.

The springs 268 will bias the pistons 2 I2 downwardly toward sleeves 66; and at low fluid pressures the pistons 2112 will have paths of reciprocation wherein the annular ports 51 will be covered by the sleeves 62 throughout the entire paths of reciprocation of those pistons. At higher pressures, the springs 268 will be unable to hold the pistons 2I2 in those paths of reciprocation; instead, those springs will yield and permit those paths of reciprocation to shift upwardly. The amounts by which those paths of reciprocation shift will be determined directly by the fluid pressures acting on the pistons; the greater those pressures the greater the shifts will be. As those paths of reciprocation shift upwardly, some, then more, and finally almost all of the fluid pumped by the pistons 2I2 will pass into ducts 266 and then pass through duct 262 into the housing I61.

The pressure-generating device of Fig. 7 will provide variable pressures and variable volumes, and the volumes delivered by that device will automatically vary as the pressures vary. In this respect the device of Fig. 7 is similar to the device of Figs. 1-5, The particular advantage of the device of Figs. 1-5 over the device of Fig. '7 is that larger and heavier springs can be used. In addition, variations in the spring pressure of one of the individual springs would be compensated for by the other springs in the device of Figs. l 5.

Fig. 8 discloses a sleeve 50 that encloses and guides a piston 2I6. This piston is solid rather than hollow; but it provides the effect of a hollow piston because it has an axially-directed port 2I8 in the surface thereof. The port 2! 8 will serve the purpose of axial bore 54, transverse bore 56, and annular port '57 of piston 52. When the path of reciprocation of piston 2H5 is located so the port 2 I 6 is wholly enclosed by the sleeve 56, piston 2I6 will pump fluid downwardly throughout its entire down stroke. However, when the path of reciprocation of that piston shifts upwardly so the port 2 I 8 is uncovered during part of the stroke of that piston, some fluidcan escape over the top of the inner periphery thereof.

15' of sleeve 50 during the downward stroke of the piston.

Fig. 9 discloses a cylinder and piston that provide the effect of a hollow piston although the piston is solid throughout. A sleeve 220, generally similar to sleeve 50, has a port 222 in one portion That port will normally be covered throughout the path of reciprocation of the piston 224; and where that is the case the piston 2% will pump fluid throughout its downward stroke. However, when the path of reciprocation of piston 224 is shifted upwardly, the undercut portion of piston 22 4 can permit fluid to enter port 2222. Consequently, at such times some of the fluid will pass upwardly through the port 222 as the piston 22 i moves through its downward stroke. A washer 226 underlies the piston 22 i, and that washer is acted upon by a spring 228.

Whereas, several preferred embodiments of the present invention have been shown and described, it should be obvious to those skilled in th art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

1. In a pressure-generating device, a cylinder, a piston reciprccable within said cylinder, a valve controlling flow of fluid into said cylinder, a second valve controlling flow of fluid out of said cylinder, a wobble plate that has a portion which forces said piston to move relative to said cylinder, a rotatable support for said wobble plate, said support being rotatable about one axis thereof, and a spring acting upon said rotatable support in a direction opposite to the action of said piston, said spring acting only on that part of the rotatable support which is coextensive with said portion of said wobble plate, whereby bending moments in said rotatable support are avoided.

2. In a pressure-generating device, a body, a bore within said body, and a seal for said body, said seal including an ring disposable within said bore in said body, a surface against which the top of said 0 ring can bear, a surface that can bear against the bottom of said O ring, and an annular projection that is on one of said surfaces and is adjacent said 0 ring, said annular projection being shorter than the thickness of said 0 ring from top to bottom, said annular projection holding said 0 ring tightly within said bore and tightly against the other of said surfaces, the end of said annular projection being spaced from the other of said surfaces.

3. In a pressure-generating device that has a stationary cylinder, a hollow piston that is reciprocable within said cylinder and that has an elongated surface that bears against said cylinder, a port in said piston that opens to said elongated surface of said piston, a valved inlet at one end of said cylinder, a valved outlet intermediate the ends of said cylinder, said inlet and outlet constituting the only ports for said cylinder, a wobble plate that forces said piston to move relative to said cylinder, said cylinder and said piston being dimensioned so said piston can have a path of reciprocation wherein said port is intermediate said valved outlet and the end of said cylinder opposite said inlet and is completely covered by said stationary cylinder throughout said path of reciprocation, said piston being capable of being shifted away from the said one end of said cylinder to a path of reciprocation wherein said port is covered by said stationary cylinder for only a part of said other path of reciprocation, said piston forcing fluid toward said valved outlet during said part of said other path of reciprocation and permitting venting of fluid through said port during the rest of said other path of reciprocation.

4.1n a pressure-generating device that has a stationary cylinder, a. hollow piston that is reciprocable within said cylinder and that has an elongated surface that bears against said cylinder, a port in said piston that opens to said elong'ated surface of said piston, a valved inlet at one end of said cylinder, a valved outlet inter-, mediate the ends of said cylinder, said inlet and outlet constituting the only ports for said cylinder, a wobble plate that forces said piston to move relative to said cylinder, said cylinder and piston being dimensioned so said. piston can have a path of reciprocation wherein said port is intermediate said valved outlet and the end of said cylinder opposite said inlet and is completely covered by said stationary cylinder throughout said path of reciprocation, said piston being capable of being shifted away from the said one end of said cylinder to a path of reciprocation wherein said port is covered by said stationary cylinder for only a part of said other path of reciprocation, said piston forcing fluid toward said valved outlet during said part of said other path of reciprocation and permitting venting of fluid through said port during the rest of said other path of reciprocation, said piston being spring-biased toward the first said path of reciprocation but responding to increased fluid pressures at said valved outlet to shift to said other path of reciprocation.

In a pressure-generating device, a cylinder, 2, piston reciprocable within said cylinder, an inlet for fluid, an outlet for fluid, a spring that biases said piston away from one end of said cylinder, a wobble plate that has one portion to force said piston toward said one end of said cylinder and has another portion to permit said spring to move said piston away from said one end of said cylinder, a rotatable support for said wobble plate, said support being rotatable about one axis thereof and being reciprocable along said axis, and a second spring biasing said rotatable support and said wobble plate toward said piston and toward said one end of said cylinder, said second spring and said rotatable support and said wobble plate normally confining said piston to a predetermined path of reciprocation responding to increased pressures on said piston to permit said piston to shift to a second path of reciprocation, said spring being in register with and acting upon the said one portion of said wobble plate.

6. In a pressure-generating device, a cylinder, a piston reciprocable within said cylinder, an inlet for fluid, an outlet for fluid, a spring that biases said piston away from one end of said cylinder, a wobble plate that has one portion to force said piston toward said one end of said cylinder and has another portion to permit said spring to move said piston away from said one end of said cylinder, a rotatable support for said wobble plate, said support being rotatable about one axis thereof and being reciprocable along said axis, and a second spring biasing said rotatable support and said wobble plate toward said piston and toward said one end of said cylinder, said second spring and said rotatable support and said wobble plate normally confining said piston to a predetermined path of reciprocation but responding to increased ressures on 17 said piston to permit said piston to shift to a second path Of reciprocation, said spring being in register with and acting upon the said one portion of said Wobble plate, said piston being hollow and having a port that opens to the exterior thereof intermediate the ends thereof, said port being covered by said cylinder throughout the said predetermined path of reciprocation but being exposed during part of said second path of reciprocation.

'7. In a pressure-generating device, a cylinder, a piston reciprocable within said cylinder, an in let for said cylinder that permits fluid to enter said cylinder, an outlet for said cylinder that permits fluid to leave said cylinder, a spring that biases said piston away from one end of said cylinder, a wobble plate that has one portion to force said piston toward said one end of said cylinder and has another portion to permit said spring to move said piston away from said one end of said cylinder, a rotatable support for said wobble plate, said support being rotatable about one axis thereof and being reciprocable along said axis, a plate that rotates about said axis but does not reciprocate along said axis, and a plurality of springs that extend between said rotatable support and said rotatable plate and bias said rotatable support for movement along said axis toward said one end of said cylinder, said plurality of spring being in register with the said one portion of said wobble plate, and interacting studs and recesses on said rotatable plate and rotatable support to confine and guide said plurality of springs, said plurality of springs and said rotatable support and said rotatable plate and said wobble plate normally confining said piston to a predetermined path of reciprocation but responding to increased pressures on said piston to permit said piston to shift to a second path of reciprocation.

8. In a pressure-generating device, a, cylinder, a piston reciprocable within said cylinder, an inlet for said cylinder that permits fluid to enter said cylinder, an outlet for said cylinder that permits fluid to leave said cylinder, a spring that biases said piston away from one end of said cylinder, a wobble plate that has one portion to force said piston toward said one end of said cylinder and has another portion to permit said spring to move said piston away from said one end of said cylinder, a rotatable support for said wobble plate, said support being rotatable about one axis thereof and being reciprocable along said axis, a plate that rotates about said axis but does not reciprocate along said axis, and a plurality of springs that extend between said rotatable support and said rotatable plate and bias said rotatable support for movement along said axis toward said one end of said cylinder, said plurality of springs being in register with the said one portion of said wobble plate, said plurality of springs and said rotatable support and said rotatable plate and said wobble plate normally confining said piston to a predetermined path of reciprocation but responding to increased pressures on said piston to permit said piston to shift to a second path of reciprocation.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,418,598 Michell June 6, 1922 1,825,691 Hall Oct. 6, 1931 1,883,601 Dauster Oct. 18, 1932 1,905,913 Kopp Apr. 25, 1933 1,933,081 Stephan Oct. 31, 1933 2,145,854 Bijur Feb. '7, 1939 2,165,696 Charter July 11, 1939 2,225,788 McIntyre Dec. 24, 1940 2,238,252 Davis Apr. 15, 1941 2,433,222 Huber Dec. 23, 1947 2,534,153 Widmer Dec. 12, 1950 2,540,328 Gray Feb. 6, 1951 

